There is known a hologram recording technique of recording information to be recorded into a holographic recording medium (hereinafter merely referred to as a “recording medium”) as an interference pattern. One method is to spatial-modulate light from a light source in accordance with the information to be recorded, to thereby generate object light and then irradiate the recording medium with the object light and reference light. The object light and the reference light interfere with each other on the recording medium, to thereby form the interference pattern. The interference pattern is recorded into a recording layer of the recording medium as a record image. At this time, the record image is recorded on the recording medium, with a marker appended, wherein the marker is a position reference of the record image.
On the other hand, in reproduction, the portion of the recording medium in which the information is recorded is irradiated only with the reference light, and detection light from the recording medium is detected by a 2-dimentional (2D) sensor to reproduce the information. At this time, in order to detect the position of the reproduction image, template matching process is performed. In the template matching process, while a template image, which is the same as a marker, is shifted by one pixel each time throughout the entire candidate area out of the reproduced record image (i.e. a reproduction image), a correlation value between the template image and the reproduction image is calculated in each position, to thereby obtain a coordinate position with the maximum correlation value.
A patent document 1 discloses the basic principle of the hologram recording technology and particularly discloses an information modulating method. Moreover, a patent document 2 discloses a marker for alignment on a semiconductor exposure apparatus, wherein the marker includes a black line whose surroundings are white or white and black stripe lines. Moreover, a patent document 3 discloses that markers made of white square pixels are appended to the four corners of a record image.    Patent document 1: Japanese Patent Application Laid Open NO. 2001-75463    Patent document 2: Japanese Patent Application Laid Open NO. 2003-92246    Patent document 3: Japanese Patent Application Laid Open NO. 2000-122012
However, if the marker appended to the record image and the original information data included in the record image are not clearly distinguished, the correlation value possibly becomes maximal in a portion where the marker is not displaced, in the template matching process. In this case, the accurate position of the marker cannot be detected, and thus the position of the record image cannot be detected.
For this reason, the following countermeasure is considered; namely, a spatial space is provided between the marker appended to the record image and the original information data included in the record image, to thereby clearly divide the marker and the original information data. However, there is such a technical problem that the space for division becomes a useless area, resulting in a reduction in a recording capacity for recording the data.
The subject to be solved by the invention includes the aforementioned problem as one example. It is therefore an object of the present invention to provide a method of and apparatus for intentionally selecting a marker which can be clearly distinguished from information data in a record image, a marker selected by such a marker selecting method, a hologram recording apparatus for and method of selecting such a marker in advance to use, a hologram reproducing apparatus for and method of using such marker, and a computer program for executing a computer.
The above object of the present invention can be achieved by a marker selecting method provided with: a two-dimensional modulating process of modulating information data in a two-dimensional manner in accordance with a specified modulation rule, to thereby obtain modulation data, in hologram recording/reproduction; a marker generating process of generating a first marker in accordance with the modulation rule, the first marker defining a position reference for correcting a position-shift of the modulation data in a recording/reproducing procedure; a calculating process of preparing a first verification image and a second verification image and of calculating a correlation value which indicates a correlation between a template image and the first verification image and a correlation value which indicates a correlation between the template image and the second verification image, the first verification image including a second marker obtained by shifting the first marker by a predetermined pixel, the second verification image including the modulation data, the template image indicating the first marker; and a selecting process of selecting the first marker by which a peak of the correlation value in the first verification image is greater than a peak of the correlation value in the second verification image.
According to the marker selecting method of the present invention, the first marker is generated by the operation of the marker generating device. The first marker is used for, for example, template matching process and to detect the position of a record image including the information data. The marker generating device generates the marker in accordance with the modulation rule in the hologram recording/reproduction.
In particular, in the present invention, the correlation value which indicates the correlation between the first verification image and the template image is calculated by the operation of the marker generating device, wherein the first verification image includes the second marker obtained by shifting the first marker by the predetermined pixel and the template image indicates the first marker. The first verification image includes not the image of the first marker itself but the image of the second marker, which is shifted by the predetermined pixel in a longitudinal direction, a lateral direction, or the like. Therefore, the first verification image includes the second marker whose positional relationship with the template image which is used in the calculation of the correlation value is shifted by the predetermined pixel. Then, the correlation value which indicates the correlation between the template image and the second verification image is calculated, wherein the second verification image includes arbitrary information data, which is used for actual recording. After that, the first marker is intentionally selected such that the peak of the correlation value in the first verification image is greater than the peak of the correlation value in the second verification image. The selected first marker is used in the actual recording operation or reproduction operation. In short, in the actual recording operation or reproduction operation, a marker image indicating the selected first marker is generated and recorded onto a hologram recording medium as record image data together with the modulation data, which includes the information data, by the operation of a two-dimensional (2D) modulating device. In the reproduction, the generated marker image is used as the template image and is used to detect a reference position for correcting an image distortion in the recording/reproducing procedure.
As described above, the marker is intentionally selected by the selecting device such that the peak of the correlation value in the first verification image is greater than the peak of the correlation value in the second verification image. In other words, the marker to which the first verification image is more similar than an image portion in the second verification image including the information data which is most similar to the marker is selected. In particular, since the first verification image includes the second marker shifted by the predetermined pixel, its correlation value is obviously lower than the correlation value of the first maker which originally has no pixel-shift. Even if such a position-shift which results in the lower correlation value is intentionally assumed, the marker which has the higher correlation value in the position where the original marker exists is selected, compared to the correlation value in the image portion which is most similar to the marker in the second verification image including the modulation data. The marker may be selected by a hologram recording apparatus or a hologram reproducing apparatus. Alternatively, the marker may be selected in advance, separately. Therefore, in the actual hologram recording or reproduction, it is possible to clearly distinguish the marker image and the record image including the modulation data obtained by 2D-modulating the information data. By this, it is no longer necessary to separate the marker image and the record image including the information data with a spatial space provided, to thereby preferably ensure the recording capacity for recording the information data. That is, the recording capacity of the holographic recording medium can be efficiently used.
In one aspect of the marker selecting method of the present invention, a similar pattern which is similar to the first marker is disposed at least one portion of the second verification image, and the selecting process selects the first marker by which the peak of the correlation value in the first verification image is greater than the peak of the correlation value in the portion of the second verification image in which the similar pattern is disposed.
According to this aspect, the marker that allows a clear distinction between the marker image and the record image including the information data is preferably selected. Therefore, it is possible to preferably receive the aforementioned various benefits.
In this aspect, if the modulation rule is different, a different pattern may be also generated for the similar pattern.
By virtue of such construction, the similar pattern can be preferably disposed in the second verification image in accordance with the modulation rule.
In another aspect of the marker selecting method of the present invention, the first verification image includes the second marker obtained by shifting the first marker by 0.5 pixel, as the predetermined pixel.
According to this aspect, as explained later in detail in an embodiment by using the drawings, the correlation value in the first verification image can be intentionally reduced. Even in this case, the selected marker realizes that the peak of the correlation value in the first verification image is greater than the peak of the correlation value in the second verification image. Therefore, the marker that allows the clear distinction between the marker image and the record image including the information data is selected. Therefore, it is possible to preferably receive the aforementioned various benefits.
In another aspect of the marker selecting method of the present invention, the first verification image includes the second marker shifted by the predetermined pixel on the basis of a pixel unit on a light receiving element used when the modulation data is reproduced.
According to this aspect, the marker is selected in view of the light receiving element mounted on the hologram recording apparatus or hologram reproducing apparatus.
In another aspect of the marker selecting method of the present invention, the first verification image includes the first marker shifted by the predetermined pixel in each of a longitudinal direction and a lateral direction.
According to this aspect, the marker that allows the clear distinction between the marker image and the record image including the information data is preferably selected. Therefore, it is possible to preferably receive the aforementioned various benefits.
The above object of the present invention can be also achieved by a marker selecting apparatus provided with: a two-dimensional modulating device for modulating information data in a two-dimensional manner in accordance with a specified modulation rule, to thereby obtain modulation data, in hologram recording/reproduction; a marker generating device for generating a first marker in accordance with the modulation rule, the first marker defining a position reference for correcting a position-shift of the modulation data in a recording/reproducing procedure; a calculating device for preparing a first verification image and a second verification image and of calculating a correlation value which indicates a correlation between a template image and the first verification image and a correlation value which indicates a correlation between the template image and the second verification image, the first verification image including a second marker obtained by shifting the first marker by a predetermined pixel, the second verification image including the modulation data, the template image indicating the first marker; and a selecting device for selecting the first marker by which a peak of the correlation value in the first verification image is greater than a peak of the correlation value in the second verification image.
According to the marker selecting apparatus of the present invention, it is possible to receive the same various benefits as those of the marker selecting method of the present invention.
Incidentally, in response to the various aspects owned by the aforementioned marker selecting method of the present invention, the marker selecting apparatus of the present invention can also adopt various aspects.
The above object of the present invention can be also achieved by a marker for defining a position reference when information data is recorded in accordance with a modulation rule in hologram recording/reproduction, wherein a peak of a correlation value which indicates a correlation between a first verification image and a template image is greater than a peak of a correlation value which indicates a correlation between a second verification image and the template image, the first verification image including the marker shifted by a predetermined pixel, the template image indicating the marker, the second verification image including the record information. That is, the marker of the present invention is a marker selected by the marker selecting method of the present invention (including its various aspects).
According to the marker of the present invention, it is possible to receive the same various benefits as those of the marker selecting method of the present invention.
Incidentally, in response to the various aspects owned by the aforementioned marker selecting method of the present invention, the marker of the present invention can also adopt various aspects.
The above object of the present invention can be also achieved by a hologram recording apparatus provided with: an appending device for appending a marker selected by the aforementioned marker selecting method of the present invention (including its various aspects) to a record image including the information data; and a recording device for recording the record image to which the marker is appended, onto a holographic recording medium.
According to the hologram recording apparatus of the present invention, it is possible to append the marker (or marker image) that allows the clear distinction from the record image including the information data, to the record image. Therefore, it is possible to preferably receive the aforementioned various benefits.
Incidentally, in response to the various aspects owned by the aforementioned marker selecting method of the present invention, the hologram recording apparatus of the present invention can also adopt various aspects.
The above object of the present invention can be also achieved by a hologram recording method provided with: an appending process of appending a marker selected by the aforementioned marker selecting method of the present invention (including its various aspects) to a record image including the information data; and a recording process of recording the record image to which the marker is appended, onto a holographic recording medium.
According to the hologram recording method of the present invention, it is possible to receive the same various benefits as those of the hologram recording apparatus of the present invention.
Incidentally, in response to the various aspects owned by the aforementioned hologram recording apparatus of the present invention, the hologram recording method of the present invention can also adopt various aspects.
The above object of the present invention can be also achieved by a hologram reproducing apparatus provided with: a processing device for performing template matching process with respect to a record image including the information data recorded on a graphic recording medium by using a marker selected by the aforementioned marker selecting method of the present invention (including its various aspects); and a reproducing device for reproducing the information data included in the record image.
According to the hologram reproducing apparatus of the present invention, the marker (or marker image) and the record image including the information data can be clearly distinguished in the template matching. Therefore, it is possible to preferably receive the aforementioned various benefits.
Incidentally, in response to the various aspects owned by the aforementioned marker selecting method of the present invention, the hologram reproducing apparatus of the present invention can also adopt various aspects.
The above object of the present invention can be also achieved by a hologram reproducing method provided with: a processing process of performing template matching process with respect to a record image including the information data recorded on a graphic recording medium by using a marker selected by the aforementioned marker selecting method of the present invention (including its various aspects); and a reproducing process of reproducing the information data included in the record image.
According to the hologram reproducing method of the present invention, it is possible to receive the same various benefits as those of the hologram reproducing apparatus of the present invention.
Incidentally, in response to the various aspects owned by the aforementioned hologram reproducing apparatus of the present invention, the hologram reproducing method of the present invention can also adopt various aspects.
The above object of the present invention can be also achieved by a first computer program for hologram recording control to control a computer provided in the aforementioned hologram recording apparatus of the present invention (including its various aspects), the computer program making the computer function as at least one portion of the appending device and the recording device. Moreover, the above object of the present invention can be also achieved by a second computer program for hologram reproduction control to control a computer provided in the aforementioned hologram reproducing apparatus of the present invention (including its various aspects), the computer program making the computer function as at least one portion of the processing device and the reproducing device.
According to each of the computer programs of the present invention, the above-mentioned hologram recording apparatus or hologram reproducing apparatus of the present invention can be relatively easily realized as a computer reads and executes the computer program from a program storage device, such as a ROM, a CD-ROM, a DVD-ROM, and a hard disk, or as it executes the computer program after downloading the program through a communication device.
Incidentally, in response to the various aspects of the above-mentioned hologram recording apparatus or hologram reproducing apparatus of the present invention, each of the computer programs of the present invention can also adopt various aspects.
The above object of the present invention can be also achieved by a first computer program product in a computer-readable medium for tangibly embodying a program of instructions executable by a computer provided in the aforementioned hologram recording apparatus of the present invention (including its various aspects), the computer program product making the computer function as at least one portion of the appending device and the recording device. The above object of the present invention can be also achieved by a second computer program product in a computer-readable medium for tangibly embodying a program of instructions executable by a computer provided in the aforementioned hologram reproducing apparatus of the present invention (including its various aspects), the computer program product making the computer function as at least one portion of the processing device and the reproducing device.
According to each of the computer program products of the present invention, the aforementioned hologram recording apparatus or hologram reproducing apparatus of the present invention can be embodied relatively readily, by loading the computer program product from a recording medium for storing the computer program product, such as a ROM (Read Only Memory), a CD-ROM (Compact Disc-Read Only Memory), a DVD-ROM (DVD Read Only Memory), a hard disk or the like, into the computer, or by downloading the computer program product, which may be a carrier wave, into the computer via a communication device. More specifically, the computer program product may include computer readable codes to cause the computer (or may comprise computer readable instructions for causing the computer) to function as the aforementioned hologram recording apparatus or hologram reproducing apparatus of the present invention.
These effects and other advantages of the present invention will become more apparent from the embodiment explained below.
As explained above, according to the marker selecting method of the present invention, it is provided with the marker generating process, the calculating process, and the selecting process. According to the marker selecting apparatus of the present invention, it is provided with the marker generating device, the calculating device, and the selecting device. Therefore, the mark that allows the clear distinction between the marker image and the record image including the information data is preferably selected.
Moreover, according to the marker of the present invention, the peak of the correlation value in the first verification image is greater than the peak of the correlation value in the second verification image. Therefore, the marker image and the record image including the information data can be clearly distinguished.
Moreover, according to the hologram recording apparatus of the present invention, it is provided with the appending device and the recording device. According to the hologram recording method of the present invention, it is provided with the appending process and the recording process. Therefore, the marker image and the record image including the information data can be clearly distinguished.
Moreover, according to the hologram reproducing apparatus of the present invention, it is provided with the processing device and the reproducing device. According to the hologram reproducing method of the present invention, it is provided with the processing process and the reproducing process. Therefore, the marker image and the record image including the information data can be clearly distinguished.